OR WAIT null SECS
a) Dechlorinate 500 mL water samples with 25 mg sodium sulphite (if free chlorine present). Acidify the samples to pH ≤ 2 with 6 N HCl.
c) Wash the SPE cartridges with 10 mL of DCM. Condition with 10 mL of methanol, followed by 10 mL of reagent water.
d) Insert the stainless steel ends of the sample transfer tubes into the sample containers. Draw the entire sample through the cartridge at a fast drop-wise rate (about 15 mL/min).
e) Dry the SPE cartridges under full vacuum for 10 min.
f) Attach pre-rinsed (5 mL EtOAc) drying cartridges (ECSS15M6) to the bottom of the SPE cartridges using cartridge adaptors (AD0000AS).
g) Place glass vials (40–60 mL) into the collection rack (VMF02125), and insert the rack into the SPE manifold.
h) Wash the sample containers with 10 mL of EtOAc. Pass 1/3 of the rinsate through the SPE cartridges using the transfer tubes. Let them soak for 1 min and then slowly pass through the SPE cartridges.
i) Repeat the elution with 15 mL of DCM.
j) Concentrate the eluate to about 0.9 mL under a gentle stream of nitrogen at 40 °C.
k) Add the internal standard and adjust the final volume to 1 mL with EtOAc. The samples are ready for gas chromatography–mass spectrometry (GC–MS) analysis.